Method of aging a display panel

ABSTRACT

The method comprises assembling the various parts of a display panel made up of rows and columns of tiny dot-like display cells and including elongated anode and cathode electrodes, filling the panel with the desired gas, and then aging the panel by turning on all of its cells in a sequential pattern and with the panel held at an elevated temperature.

[451 Aug. 29, 1972 United States Patent Holz .315/169 Ogle 8/1971Kupsky.................

[54] METHOD OF AGING A DISPLAY PANEL [72] Inventor: George E. Holz,North Plainfield,

[73] Assignee: Burroughs Corporation, Detroit,

Primary Examiner-John F. Campbell Assistant ExaminerRichard BernardLazarus Mich.

AttorneyKenneth L. Miller, Robert A. Green, George L. Kensinger andCharles S. Hall [22] Filed: March 24,1971

21 Appl.No.: 127,458

[57] ABSTRACT The method comprises assembling the various parts of adisplay panel made up of rows and columns of tiny dot-like display cellsand including elongated anode and cathode electrodes, filling the panelwith the desired gas, and then aging the panel by turning on all of itscells in a sequential pattern and with the panel held at an elevatedtemperature.

MwmO/m ww l fi 3101 y B B M H m7 2 a w 0 2 W 0 1 mums 1N m3 nnu mmmlw mfi mum mama l we C d 8mm UIF 218 555 8 Claims, 2 Drawing Figures [5 6]References Cited UNITED STATES PATENTS 3,384,770 5/1968Vodicka...................29/25.l3

PATENTED ms 2 9 1912 saw 1 0r 2 v BOGEORGE E. HOLZ ATTORNEY METHOD OFAGING A DISPLAY PANEL BACKGROUND OF THE INVENTION One type of displaypanel processed according to the present invention is known as aSELF-SCAN panel, and these panels include large numbers of tinygasfilled cells. These panels have been available commercially for sometime, and have been manufactured generally satisfactorily by methodsnormally employed in the gas tube art in manufacturing display tubeshaving relatively large number cathodes. In general, the methodcomprises assembling the various parts and sealing them together,filling the panel with the desired gas, aging by operating the panel atroom temperature but at higher than normal operating currents, andfinally, introducing mercury to minimize cathode sputtering duringnormal panel operation. Although this method of manufacturing andprocessing a. display panel produces good panels, problems arise becauseaging is performed without mercury present in the gas filling, and thisis done because, with the prior art method, it is not possible toachieve proper aging with mercury present. However, when a display panelis aged without mercury, there is some cathode sputtering onto the wallsof the panel cells, and this reduces the viewing angle of the cells tosome extent. In addition, this aging method produces cathodes which,although their operation is generally satisfactory, have surfacenon-uniformities which produce non-uniformities in cathode glow. This isa feature which, although it does not render panels unusable, should beeliminated. In addition, it has been found that occasionally thecathodes in display panels cannot be aged at all by prior art methods.

SUMMARY OF THE INVENTION Briefly, the invention comprises assembling allof the parts of a display panel, filling the panel with the desired gas,and aging the panel at elevated temperature.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective exploded view of adisplay panel prepared according to the method of the invention; and 1FIG. 2 is a sectional view, along the lines 2-2 in FIG. 1, showing thepanel assembled.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A display panel 10, embodyingthe invention, is known as a SELF-SCAN panel and includes a plate ofinsulating material, such as glass or ceramic, having a plurality ofparallel slots 30 formed in the top surface thereof. Electrodes 40,which are used as scanning anodes in one mode of operation of the panel,are seated in each of the slots 30, and electrodes 50, of stainlesssteel or the like, used as scanning cathodes, are seated on or in thetop surface of plate 20. Each cathode electrode 50 crosses each anodeelectrode 40, and each crossing defines a scanning cell 60. The cathodesinclude rows of tiny apertures 70, each of which is located at ascanning cell. The scanning cells are arrayed in rows and columns, andeach cathode 50 is oriented along a vertical column of scanning cells inthe panel as illustrated.

The panel 10 includes an insulating plate disposed over the cathodes 50and having apertures or display cells arrayed in rows and columns, witheach cell 90 being in operative relation with and positioned over acathode aperture 70 and a scanning cell 60. Display anode wires aredisposed on or in the top surface of the insulating plate 80, and eachis aligned with a row of display cells 90. A glass cover plate completesthe panel.

A glass tubulation is secured to the base plate 20 and communicates withthe interior of the panel through a hole in plate 20. A capsulecontaining a droplet of mercury is suitably supported in the tubulationnear base plate 20. The capsule 140 is preferably of infrared absorbingglass.

In practicing the method of the invention, all of the parts describedare properly cleaned and assembled and secured together by means of anairtight seal (FIG. 2) formed along the periphery thereof by means of aglass frit or the like. A particularly suitable material for the seal isknown as Pyroceram, and this material is applied as a fluid mixture ofpowdered glass in a suitable binder or carrier. With the parts suitablyheld together, the fluid cement is placed along the aligned edges of thepanel parts, and the assembly is then heated to fonn the desired sealupon cooling. After the seal has been formed, the panel is baked andevacuated through the tubulation 120, and then it is filled with thedesired gas through the tubulation.

The gas filling may be any of the well known ionizable gases such asneon, argon, xenon, etc., singly or in combination. In addition, the gasused is preferably a Penning mixture in which the gases of the mixturehave related energy levels such that the metastable atoms of one gasproduce ions of the other gas. Neon and xenon comprise a particularlyeffective Penning mixture. The gas pressure at room temperature ispreferably between 50 and 350 Torr or more, and Torr has been found tobe a convenient pressure.

After the display panel has been assembled and filled with the desiredgas, the tubulation 120 is sealed ofi below the mercury capsule, asrepresented by dash lines 170, and the mercury capsule is opened torelease the mercury into the tubulation. This may be accomplished byheating the capsule with infrared radiation or in any other suitablemanner. Next, the panel is aged by firing all of the scanning anddisplay cells in any suitable manner. In one suitable arrangement,operating potentials are applied to the anode electrodes 40, and each ofthe scanning cathodes 50 has potential applied to it, in turn, so thatthe scanning cells are turned on column by column. At the same time,generally positive potentials are applied to all of the display anodes90 so that, as each of the columns of scanning cells is turned on, eachof the columns of display cells is also turned on.

The cell currents are of the order of 1 milliampere in the scanningcells and 2 milliamperes in the display cells. This procedure isperformed with the panel held at an elevated temperature of the order of120C. for a period of 12 to 48 hours. The heating may be achieved byplacing the panel in an oven or in any other suitable manner. As noted,this aging step may also be performed cell by cell or row by row, or inany other suitable cell pattern. After this aging process has beenperformed, the panel is ready for use.

The aging currents, the aging temperature, and time of aging may bevaried as can be readily determined by those skilled in the art. Theaging parameters set forth above are typical and are found to besuitable for one type of display panel such as the Burroughs SSR 1000panel. Panels of this type include, typically, gas display cells havinga diameter of the order of mils and a depth of the order of 30 to 50mils, cathodes and anodes of a nickel-chrome-iron alloy, and gaspressure of the order of 170 Torr at room temperature. The sameprinciples of aging can be applied to other types and sizes of displaypanels and display devices.

One of the most important advantages of the present invention resides inthe fact that a display panel can be aged after mercury is introducedinto the display cells thereof, although this was not feasible in theprior art. With such an arrangement, cathode sputtering during aging iseither prevented, or it is so minimal that it is of no effect. Thus,there is no deposit of sputtered material on the display cell walls, andthe viewing angle is a maximum. In addition, aging with mercury in thegas atmosphere produces cathode electrodes which are impregnated with auniform, permanent coating of mercury, and this in turn providesimproved low temperature cathode life and greater uniformity of glowacross a cathode. In addition, it has been found that some panels whichcould not previously have been aged at room temperature can now be aged.This appears to be because, at elevated temperatures and withconsiderable mercury vapor in the gas, the breakdown voltage of eachcell increases. However, the sustainingvoltage of each cell remainsgenerally constant so that the margin between the two voltages increasesand the panel can be aged harder and thus more effectively.

What is claimed is:

l. The method of making multi-cell, gas-filled display panels comprisingthe steps of assembling a plurality of insulating plates and electrodesto form a gastight envelope including a large number of tiny, cells,each having operating electrodes,

filling said envelope with a gas filling and a quantity of mercury, and

heating the panel in a chamber while turning on and operating each ofsaid cells with said panel at an elevated temperature above 90 C. 2. Themethod defined in claim 1 wherein said cells are turned on and operatedcyclically.

3. The method defined in claim 1 wherein said elevated temperature is ofthe order of 120 C. and said cells are turned on and operated cyclicallyat said temperature for a period of about 12 to about 48 hours.

4. The method defined in claim 1 wherein said elevated temperature is ofthe order of 120 C., and said cells are turned on and operatedcyclically at said temperature and at a current of the order of 2milliamperes for a period of about 12 to about 48 hours.

5. A method of making a multicell, gas-filled display panel comprisingthe steps of assembling a first base plate having a plurality of slotswith a first array of first electrodes seated in said slots and a secondarray of apertured second electrodes seated on the top surface thereofand oriented at to said first electrodes.

said first and second electrodes defining a first array of firstscanning cells, seating an apertured insulating plate on said secondarray of electrodes,

the apertures in said second plate being arrayed in rows and columns andcomprising display cells, each aligned with an aperture in said secondelectrodes,

seating an array of third electrodes on said second plate, each thirdelectrode being aligned with a row of said apertures in said secondplate,

seating a glass cover plate on said second plate,

sealing together said first plate, said second plate,

and said cover plate to form a gastight envelope, filling said envelopewith a gas filling and a quantity of mercury, and

heating the panel in a chamber while turning on and operating each ofsaid scanning cells and display cells with said panel at an elevatedtemperature above 90 C.

6. The method defined in claim 5 wherein said scanning and display cellsare turned on and operated cyclically.

7. The method defined in claim 5 wherein said elevated temperature is ofthe order of C. and said scanning and display cells are turned on andoperated cyclically at said temperature for a period of about 12 toabout 48 hours.

8. The method defined in claim 5 wherein said elevated temperature is ofthe order of 120 C., and said scanning and display cells are turned onand operated cyclically at said temperature and at a current of theorder of 2 milliamperes for a period of about 12 to about 48 hours.

1. The method of making multi-cell, gas-filled display panels comprisingthe steps of assembling a plurality of insulating plates and electrodesto form a gastight envelope including a large number of tiny cells, eachhaving operating electrodes, filling said envelope with a gas fillingand a quantity of mercury, and heating the panel in a chamber whileturning on and operating each of said cells with said panel at anelevated temperature above 90* C.
 2. The method defined in claim 1wherein said cells are turned on and operated cyclically.
 3. The methoddefined in claim 1 wherein said elevated temperature is of the order of120* C. and said cells are turned on and operated cyclically at saidtemperature for a period of about 12 to about 48 hours.
 4. The methoddefined in claim 1 wherein said elevated temperature is of the order of120* C., and said cells are turned on and operated cyclically at saidtemperature and at a current of the order of 2 milliamperes for a periodof about 12 to about 48 hours.
 5. A method of making a multi-cell,gas-filled display panel comprising the steps of assembling a first baseplate having a plurality of slots with a first array of first electrodesseated in said slots and a second array of apertured second electrodesseated on the top surface thereof and oriented at 90* to said firstelectrodes. said first and second electrodes defining a first array offirst scanning cells, seating an apertured insulating plate on saidsecond array of electrodes, the apertures in said second plate beingarrayed in rows and columns and comprising display cells, each alignedwith an aperture in said second electrodes, seating an array of thirdelectrodes on said second plate, each third electrode being aligned witha row of said apertures in said second plate, seating a glass coverplate on said second plate, sealing together said first plate, saidsecond plate, and said cover plate to form a gastight envelope, fillingsaid envelope with a gas filling and a quantity of mercury, and heatingthe panel in a chamber while turning on and operating each of saidscanning cells and display cells with said panel at an elevatedtemperature above 90* C.
 6. The method defined in claim 5 wherein saidscanning and display cells are turned on and operated cyclically.
 7. Themethod defined in claim 5 wherein said elevated temperature is of theorder of 120* C. and said scanning and display cells are turned on andoperated cyclically at sAid temperature for a period of about 12 toabout 48 hours.
 8. The method defined in claim 5 wherein said elevatedtemperature is of the order of 120* C., and said scanning and displaycells are turned on and operated cyclically at said temperature and at acurrent of the order of 2 milliamperes for a period of about 12 to about48 hours.